1. Field of the Invention
This invention relates to a water hammerless valve with a pneumatically-operating valve for opening and closing the fluid channel through the pneumatic actuator operation to control opening of a fluid channel caused by the occurrence of a water hammer.
2. Description of the Related Art
It is well known that the water hammer results from a sudden closure of a valve placed in a pipe in which fluid such as water passes. The water hammer causes rapid increase in pressure along upstream from the valve closing point, which results in a pressure wave. The wave is transmitted within the pipe at a constant speed, and it also vibrates the pipe or makes the noise.
When the water hammer occurs in the pipe including the pneumatically-operating valve for opening and closing the fluid channel through the pneumatic actuator operation, a spring provided in the actuator is compressed by the water hammer pressure to move the stem upward. Therefore, the fluid channel is forced to be slightly opened to cause a backward flow of fluid.
An effective method to prevent the fluid channel from opening by the water hammer pressure might be a forcible pressure applied to the stem from upward to interfere the valve opening.
For example, Japanese utility model publication Jitsugan S58-48479 (Jitsukai S59-152255) discloses this kind of a prior art. In the technique disclosed therein, a cylindrical part is provided with a male thread in the upper stem. The cylindrical part is screwed with a bolt, wherein the bolt compresses the upper end of the stem.
However, the technique disclosed therein requires to press the stem with the bolt manually screwed by operators in the field, which results in complicated operation. It is difficult for operators to take immediate responses in an emergency situation.
Japanese utility model publication Jitsugan S63-135498 (Jitsukai H02-56984), on the other hand, discloses another valve comprising a stopper configured to make the valve opening constant, a stopper actuator configured to activate the stopper, and a remote controller configured to transmit a remote signal to the stopper actuator. The stopper presses the upper end of the stem.
The technique disclosed in Japanese utility model publication Jitsugan S63-135498 (Jitsukai H02-56984) is superior to the one in the technique disclosed in Japanese utility model publication Jitsugan S58-48479 (Jitsukai S59-152255) in terms of the remote control availability. However, the disclosed technique is to maintain to open the valve in certain degree in a regular situation. This does not prevent the water hammer pressure from opening the fluid channel when the valve is closed.
In order to solve the above-described problems in the prior arts, the present invention provides a water hammerless valve which automatically prevents the stem from moving upward when the water hammer occurs. Using the water hammerless valve, it is possible to control opening of the fluid channel using the pneumatically-operating valve configured to open and close the fluid channel through the pneumatic actuator operation.